Chapter 5 Dimerization of unsaturated fatty acids/ methyl ...shodhganga.inflibnet.ac.in/bitstream/10603/25187/2/13. chapter 5.pdf · Ph. D. Thesis, Priya S. Deshpande, NMU, Jalgaon,

Ph. D. Thesis, Priya S. Deshpande, NMU, Jalgaon, 2013

178

Chapter 5

Dimerization of unsaturated fatty acids/ methyl esters and alkali fusion

of ricinoleic acid

5.1 Background and objectives of investigations

The diverse and significant applications of dimer acids are presented under section

1.4 of Chapter 1. They have some unique properties and the chemical nature of these

acids can alter or modify condensation polymers in reference to elasticity, flexibility,

impact strength, hydrolytic stability, hydrophobicity and lower glass transition

temperatures. Therefore dimer acids present a special niche market area. Sebacic acid

finds variety of industrial uses in the field of plasticizers, lubricants, hydraulic fluids,

cosmetics etc. It is also used for the synthesis of polyester and polyamide and as an

intermediate for antiseptics. 2-Octanol is the feedstock for the production of flavouring

compounds. In spite of excellent commercial potential, the research papers and reports on

synthesis of these renewable oleochemicals are few in number. This reflects the necessity

of additional R & D inputs.

5.1.1 Synthesis and characterization of dimerized unsaturated fatty acids/ esters

The synthesis of dimer acids is subject of many international patents1-2

. The

product, as per patent and commercial literature, is well known in US industries since

1950. On the other hand, the manufacture of dimer acid is yet to commercialize in India,

barring some isolated but unsuccessful attempts e.g. Jayant Agro-organics Ltd., Mumbai.

US industries use tall oil as raw material for manufacture of dimer acid, which is not

available in India. Hence, it is essential to establish the dimer acid manufacturing process

based on indigenous raw materials. Thus DCO (dehydrated castor oil) and soyabean oil,

which are easily available at moderate cost in India, were selected as feedstock for dimer

acid synthesis. Oleic acid which was earlier used as raw material for epoxidation

(Chapter 3), was also examined as feedstock for dimer acid synthesis. High energy

consumption, low yield, poor colour etc. are some of the major drawbacks of clay

catalyzed, high temperature (> 3000C) and high pressure (400 psi) route used for the

industrial production of dimer acids. Hence accomplishment of dimerization at lower

reaction temperature and pressure was the major objective of investigations on acid

activated clay catalysed synthesis of dimer acids from oleic acid/ DCO fatty acids and

soya fatty acids/ methyl esters. Two routes were explored: high pressure clay catalysed


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dimerization of fatty acids and low pressure clay catalysed dimerization of fatty esters.

The experimental conditions (multistage synthesis, catalyst concentration, reaction period,

temperature, steam pressure etc.) were optimized for higher yield (> 60%) and lighter

Gardner colour (< 5) of dimer acids.

5.1.2 Synthesis and characterization of 2-octanol and sebacic acid by alkali fusion of

sodium ricinoleate

Castor oil is an important non-edible renewable resource which should be

exploited as far as possible so that the edible oils can be freed for human consumption.

This is especially important in developing countries like India where food security poses a

challenge. In many countries with little or no petrochemical feedstock, castor oil will come

in handy as a versatile resource for industrial applications.

There are very few publications on synthesis of sebacic acid by alkali fusion of

castor oil3-6

. The sebacic acid yields were reported to be low. The present study reports

investigations on establishment of suitable reaction conditions and catalysts for alkali

fusion of ricinoleic acid- the principal fatty acid present in castor oil. Different transition

metal oxides were searched for their suitability as alkali fusion catalyst. One of the major

changes in material properties with reduction in size to nanometre range has been the

enormous increase in surface area per unit mass/ volume. The application of this concept

in catalysis, thus, results in production of catalysts of high activity and selectivity. Hence

in present study, zinc oxide was obtained in nano size form by using impinging solution

spray mode of synthesis and the resulting nanomaterial was explored as a catalyst for

alkali fusion of ricinoleic acid.

5.2 Raw materials and chemicals

Oleic acid and ricinoleic acid were procured from s d fine Chem. Ltd., Mumbai

and Jayant Agro-organics Ltd., Mumbai, respectively. Soyabean and castor oil were

purchased from local market. Their fatty acid composition and other characteristics have

been reported in Table 3.1 of Chapter 3. Dehydration of castor oil was carried under

nitrogen atmosphere at 2300C for 2 hrs. It was accomplished by using two different

catalysts: conc. H2SO4 catalysing formation of product designated as DCO-I and

combination of sodium bisulphite and sodium sulphite catalysing the formation of product

designated as DCO-II, respectively. DCO/ soya fatty acids (FA) and methyl esters

(FAME) were prepared using procedure described under section 2.3.1 of Chapter 2.

Table 5.1 presents characteristics of these renewable feedstock.


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Table 5.1 Physicochemical characteristics of raw materials used for dimerization and

alkali fusion

Feedstock RI AV HV IV

Oleic acid 1.450 193.76 -- 98.20

Methyl oleate 1.4521 1.5 -- -

Soya FA 1.4583 203.5 -- --

Soya FAME 1.4615 0.5

Ricinoleic acid 1.4703 175 150 88.1

DCO FA-I 1.472 205.4 -- 127.3

DCO FA-II 1.4805 204.6 -- 132.5

Catalysts for dimer acid synthesis: Fuller earth (mesh size 100), obtained from s. d. fine-

Chem. Ltd., Mumbai, was subjected to thermal activation at 1100C for 2 hrs and acid

activation by treatment with conc. H2SO4.

Catalysts for alkali fusion of ricinoleic acid: The transition metal oxides examined as

catalysts were lead monoxide, barium sulphate, zinc oxide and nano zinc oxide.

Preparation of nanozinc oxide

Zinc oxide nanoparticles were synthesized by carrying Tween 80 (polyoxyethylene (80)

sorbitan monooleate) stabilized caustic hydrolysis and oxidation of zinc nitrate solution in

impinging solution spray reactor, patented by Mishra and co-workers7. The use of this

reactor, incorporating external mixing two fluid nozzle for atomization of zinc nitrate

solution as well as caustic solution, and the corresponding procedure have been already

described under section 2.3.3 of Chapter 2 for the synthesis of nano lead chrome. Fig.5.1

portrays FESEM image of synthesized nano zinc oxide at a scale of 500 nm and provide

the evidence of the size stabilisation of zinc oxide in nanometer range. The FESEM

analysis in fact, substantiates the superiority of impinging solution spray in providing thin

film oxidation zone and the role played by Tween 80 surfactant in size and morphology

stabilisation of zinc oxide nanoparticles during their synthesis. The EDX spectrum

presented in Fig. 5.2 supported confirmation of zinc oxide formation (Zn and O peak) by

caustic hydrolysis and oxidation of zinc nitrate solution. The nitrogen peak showed

negligible presence.


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Fig. 5.1 FESEM image of nano zinc oxide

Fig. 5.2 EDX spectrum of nano zinc oxide

5.3 Experimental methodology

5.3.1 Medium pressure clay catalysed dimerization of oleic acids, DCO fatty acids,

and soyabean fatty acids

The feed mixture composed of fatty acids, acid activated clay catalyst and water at specific

ratio, as given under Table 5.2 and Table 5.3, was transferred to a ½ lit high-pressure

stainless-steel autoclave (Amar Engineering, Mumbai) equipped with a magnetic


182

motorised drive and an electrical heating system coupled with PID temperature controller.

Air above the reaction mixture was vented by nitrogen flushing under vacuum. Nitrogen

flow and vacuum was discontinued and the pressure vessel was sealed. The reaction

mixture was heated to the desired temperature (190-2500C) and maintained there at for

given period (1-5 hrs). The reaction mixture was cooled to room temperature and the

catalyst was separated from the crude product by filtration through a 60 mm fritted funnel

at 600C in oven. The catalyst residue was washed with acetone (50 ml) to recover the

adsorbed product. The filtrate- polymerized fatty acids were fractionated as monomer

(distillate) and dimer and higher oligomers (residue) by high vacuum distillation under

nitrogen flow. Distillation temperature and vacuum (1-5 mm Hg) were recorded and the

weight of both distillate (monomer) and residue (dimer + trimer) was determined.

Refractive index (RI), TLC (developing solvent- ether:hexane:acetic acid::6:4:1)

and FTIR analysis were used as a qualitative tool for confirmation of dimerization. Colour

of the product was recorded using Gardner colour. In addition, AV, IV and SV

characteristics of the product were recorded.

5.3.2 Clay catalysed dimerization of soyabean FAME and methyl oleate under

nitrogen atmosphere

The feed mixture composed of FAME and clay catalyst (no water was charged) at specific

ratio, as given under Table 5.2 and Table 5.3, was placed into a 500 ml three neck flask

equipped with a magnetic stirrer and an electrical heating system coupled with energy

regulator. After ensuring thorough dispersion of catalyst, nitrogen sparging was initiated

through the mixture followed by heating the reaction mixture to the given temperature

(230-2500C). Constant N2 bubbling rate was maintained throughout the reaction period (5-

6 hrs) and during cooling.

The corresponding results of both processes are recorded in Table 5.2 and Table

5.3.

5.3.3 Synthesis of 2-octanol and sebacic acid by alkali fusion of sodium ricinoleate

Preparation of sodium ricinoleate:

In situ neutralisation of ricinoleic acid was carried out by refluxing the mixture of

ricinoleic acid and 2 N alc. NaOH for 4 hrs in a 500 ml four neck flask equipped with

mechanical stirrer and reflux condenser. The alcohol was thereafter removed under

reduced pressure to obtain sodium ricinoleate.


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Alkali fusion of sodium ricinoleate

Reaction set up: The reaction assembly consists of 500 ml four neck flask supported with

electrical heating system with energy regulator and mechanical stirrer with speed

controller. One neck carries thermometer pocket to record reaction temperature. The other

neck was connected with Claisen head, spiral condenser with chilled water circulation and

receiver. The thermometer placed in thermometer pocket of claisen head measures the

temperature at which 2-octanol (by product of alkali fusion) gets distilled from the

reaction mixture.

Alkali fusion process: The reactor was charged with sodium ricinoleate, NaOH and heavy

paraffin oil at 2:1:6 wt ratio. The reaction mixture was heated to 2500C and maintained

there at for 6 hrs under distillative set up. TLC [developing solvent- benzene:acetic

acid:water::5:4:1 and visualization of spots using bromocresol green solution under

heating], FTIR and NMR analysis were conducted to assess the completion of the reaction.

2-Octanol was separated from the reaction mixture by in situ distillation.

Separation and purification of sebacic acid from the bottom product: The solid

product from the reactor was diluted with hot water in a glass beaker and acidified to pH

6.0 with conc. hydrochloric acid. The floating oily layer carrying white mineral oil and

monobasic fatty acids was recovered using separating funnel. The remaining aqueous

layer was acidified to pH 2.0 using conc. hydrochloric acid and then cooled. The white

solid was washed with warm water. The sebacic acid was extracted using ethanol and the

solvent was recovered using rotary evaporator. Recrystalization from ethanol afforded the

pure product. Purity of sebacic acid was further confirmed by determining its acid value

and melting point.

5.4 Analytical and Instrumental techniques for characterization of dimer acids, 2-

octanol and sebacic acid

Estimations of Acid value (AV), Hydroxy Value (HV), Iodine Value (IV), and

Saponification Value (SV) were performed using the procedures given under section

2.4.1.1, 2.4.1.2, 2.4.1.3, and 2.4.1.4, respectively of Chapter 2.

Refractive Index (RI): RI analysis of Dimerized products was carried using Abbe

Refractometer.

Colour (Gardner): It was determined by matching visually the colour of the product with

calibrated colour glasses in Gardner Colour Comparator.

FTIR spectroscopy: FTIR analysis was performed using procedure and instrument

described under section 2.4.2.1 of Chapter 2.


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1HNMR spectroscopy: Model AVANCE III 400 Ascend Bruker, BioSpin International

AG, Switzerland was used for NMR analysis.

FESEM and EDAX: FESEM and EDAX analysis were performed using equipment setup

and procedure outlined under section 2.4.2.6 of Chapter 2.

5.5 Results and discussion

5.5.1 Clay catalysed dimerization of unsaturated fatty acids/ esters

Two different feedstocks were examined, monounsaturated oleic acid and

polyunsaturated soya/ DCO fatty acids. These two feedstocks follow different routes

(Diels Alder route and hydrogen exchange route)8,9

for dimerizations owing to the

differences in number of double bonds. In all, 14 different batches were conducted to

understand the influence of nature of feedstock, reaction temperature (T), holding period

(t) and clay catalyst loading on progress of dimerization.

5.5.1.1 Dimerization of oleic acid/ methyl oleate

Table 5.2 reports results of dimerization of oleic acid and methyl oleate. TLC

analysis, which exhibited 3 distinct spots-monomer, dimer and trimer, iodine value (IV)

and refractive index (RI) analysis formed the basis of understanding of the progress of the

reaction. Retention of acid value (AV) and saponification value (SV) of dimer close to

those of oleic acid indicated the success in control of decarboxylation reactions during

dimerization. There were marked increases in the RI with rise in reaction time t and

temperature T. These increases in RI with t and T are the indicative of rise in the viscosity

and molecular weight with dimerization10,11

. Evaluation of results of batch D1 against

those of D2 reflected the influence of increase in reaction temperature on rise in RI. But

high reaction temperature caused darkening of product. Moreover, slight drop in AV and

SV of dimer acid was observed. Batch D3 was conducted for longer reaction period but

with reduced catalyst quantity. Extended reaction period compensated for lower catalyst

usage as evidenced by slight increase in RI over that of batch D2. Lower catalyst usage

permitted better control of decarboxylation reaction for same steam pressure and higher

yield (lower product loss during filtration). The extended period, on the other hand,

resulted in higher energy requirement. There was also marginal rise in colour due to longer

holding time at high temperature. In order to reduce the energy consumption, two stage

synthesis- first stage of high temperature and second stage of lower temperature (batch

D4) was planned. Dimerization is a two step process8: the first stage is slow

(isomerisation, rearrangement) and requires higher temperature. Second stage is formation


185

Table 5.2 Clay catalysed dimerization of oleic acid and methyl oleate

IV of O.A. = 98.2, RI of O.A. = 1.450, RI of methyl oleate = 1.4521

Dimerization parameters Characterization of crude Dimerized

product

Batch Catalyst

(wt%)

Temp.

(0C)

Time

(hr)

Steam

pressure

(psig)

AV SV IV RI Gardner

Colour

D1 2 220 1 350 186.4 195.1 73.6 1.454 2

D2 2 240 1 520 182.1 192.7 73.2 1.456 5

D3 1.2 240 5 500 188.4 198.5 74.8 1.457 6

D4 1.2

240

(1.5hr),

200 (1hr)

2.5 500-240 181.6 194.4 71.5 1.457 4

D5 (Methyl

oleate) 5 250 6

Under N2

atm. - 187.2 83.8 1.458 1

Fig. 5.3 FTIR overlay spectra of a) oleic acid, b) oleic acid dimer (D4), c) methyl

oleate dimer (D5), d) soya FAME dimer (D9) and e) soya FA dimer (D8)


186

of acyclic dimer; it is relatively fast and could be accomplished at lower temperature. The

overall benefit of two stage synthesis is the reduction in reaction period and improvement

in the product colour while retaining product Characterizations similar to those of batch

D3 (identical RI). Thus batch D4 represented the best optimisation with reference to the

quality of dimer and overall process economics.

Dimerization of methyl oleate required employment of higher reaction temperature

and longer reaction period to attain the similar extent of dimerization. The only advantage

with use of methyl oleate as feedstock for dimerization is the feasibility of conduction of

reaction at atmospheric pressure. The colour of the dimer was also lighter.

FTIR spectra of oleic acid, Dimerized oleic acid and methyl oleate dimer have

been depicted in Fig. 5.3. Oleic acid spectrum showed stretching frequency at 2926 cm-1

and 3005 cm-1

due to =CH- alkene group while spectrum of oleic acid dimer exhibited

2854 cm-1

and 2924 cm-1

corresponding to the -CH- alkane stretching and 1363-1458 cm-1

-CH- alkane bending frequencies. The peak at 1654 cm-1

corresponding to C=C stretching

frequency in oleic acid IR spectrum was disappeared in dimer acid spectrum which

provided the confirmation of the dimerization of oleic acid and methyl oleate.

5.5.1.2 Dimerization of soya fatty acids/ methyl esters and DCO fatty acids

Table 5.3 reports the results of dimerization of soya and DCO fatty acids.

Dimerization of soya fatty acids at 2300C for 3 hrs (batch D6) resulted in yield of dimer at

13% after distillation. Addition of acid activated clay catalyst @ 4% (batch D8)

accelerated the dimerization reaction for same reaction T and t. Thus one observed 80.8%

rise in yield over that for batch D6. There was slight drop in AV. Batch D8 was conducted

at lower reaction temperature of 1900C; other parameters were same as those maintained

for batch D7. The product yield and RI was marginally declined. On the other hand,

improvement in product colour was noticed. Thus when it is essential to obtain better

product colour at reduced energy consumption, batch D8 is preferred to batch D7. Batch

D9, conducted using soya methyl ester, reported lowest dimerization yield (10%) and

lower RI (1.467) in spite of higher catalyst loading and extended reaction period. The

colour of the dimer, however, was superior and distillation of dimer was feasible at lower

temperature. The results on dimerization of soya FAME and methyl oleate have indicated

the necessity of employment of more effective activation of clay catalyst or altogether

different catalyst.

FTIR spectra of dimerized soya fatty acids and FAME have been shown in Fig.

5.3. Replacement of =CH- alkene stretching frequencies by -CH- alkane stretching and -


187

CH- alkane bending frequencies and the disappearance of C=C stretching frequency in

dimer acid IR spectrum proved the formation of dimer.

For similar reaction conditions, dehydrations of castor oil (categorised as A and B),

were accomplished by employing two different sets of dehydration catalysts- conc. H2SO4

and sodium sulphite + sodium bisulphite. Dehydration of castor oil removes hydroxyl

group at 12th

position of ricinoleate in combination with hydrogen at 11th

or 13th

position

yielding, thus, conjugated or nonconjugated double bond configuration, respectively.

Second catalyst accelerated the dehydration of castor oil (DCO-II) for higher RI (higher

conjugation/ trans isomerisation) and IV (more completeness of dehydration) [Table 5.1].

Taking clue from batch D6 (blank reaction for soya FA), dimerization of DCO FA-I was

performed at higher temperature of 2200C for longer duration of 4 hrs (batch D10). It

resulted in enormous rise in yield over batch D6 (353.8%). Besides employment of higher

temperature and extended reaction period, change in feedstock was also responsible for the

increase in dimerization yield. The superiority of DCO over soyabean fatty acids as

dimerization feedstock was primarily due to the presence of conjugated fatty acids in

former feedstock. Diels Alder dimerization of polyunsaturated fatty acids like DCO/ soya

fatty acids is a two step reaction- conjugation (slow, first order rate determining step)

followed by cyclisation to yield dimer (fast, second order reaction)8,9

. D11 and D12

represented two catalyzed short duration process versions of blank run D10: batch D11

employed lower catalyst loading at higher reaction temperature (but lower than blank run

temperature of 2500C) while batch D12 was operated at lower temperature and higher

catalyst loading. The results of the two batches in terms of RI and dimer yield were found

to be identical. Thus the two process variations D11 and D12 provided options to the

manufacturer: either operate at lower temperature and take the benefit of reduced energy

consumption or perform batch at lower catalyst usage and achieve better colour and ease

of filtration. The dimerization of DCO-II was performed at two different catalyst loadings

2% (batch D13) and 4% (batch D14). For same reaction period (t) of 3 hrs and temperature

(T) of 2200C, doubling of catalyst loading permitted rise in dimerization yield by 3.2%.

However the rise in yield was not proportionate and even batch D13 could be explored as

better process option. Comparison of results (RI and % yield) of batch D13 with those of

batch D11 established the supremacy of DCO-II as feedstock over DCO-I; former carried

higher magnitude of unsaturation (high IV) and probably higher conjugation/ trans isomers

as reflected through RI values (Table 5.1). Thus the synergistic combinations of sodium


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bisulphite and sulphite exhibited better catalytic effectiveness over conc. H2SO4 in terms

of conjugation isomerisation during dehydration of castor oil.

Thus, the overall results in Table 5.2 and 5.3 demonstrated the control of

decarboxylation at lower steam pressure. DCO fatty acids yielded more dimer than

soyabean fatty acids and oleic acid under similar conditions (catalyst concentration,

temperature, time). Dimerization of DCO fatty acids achieved 60-65% yield at lower

catalyst usage, (2-4%) moderate reaction temperature (1800-230

0C) and shorter duration of

3 hrs. DCO with high conjugation (DCO-II) gave more yield of dimer than one with less

conjugation (DCO-I). Another important consideration is the colour of the dimerized

product. Very marginal colour deepening could be observed at the end of the reaction. The

reaction product at the end of 65% conversion was pale yellow with Gardner colour 7.

This can perhaps be further improved by using appropriate additives such as antioxidants

or carbon bleaching. The results also displayed the diversity of options that manufacturers

can exercise- reduced catalyst loading at higher reaction temperature or lower reaction

temperature at higher catalyst loading. Moreover the results represented the suitability of

indigenous non edible materials such as DCO as feedstock for dimer acid production in

India.

5.5.2 Alkali fusion of sodium ricinoleate

As per the mechanism of alkali fusion of castor oil illustrated under section 1.5 of

chapter 1 (Fig. 1.9), the presence of suitable catalyst, which may work as oxygen donor,

favours the oxidation reaction of aldehyde of decanoic acid. The traditional preparation

process of sebacic acid based on high temperature, red lead catalysed alkali fusion of

ricinoleic acid, due to the use of thinner o-cresol and toxic catalyst lead oxide, shows

serious environmental pollution and toxicity concerns emphasizing the need for

establishment of alternative cleaner process. Moreover the use of red lead catalyst affects

product colour. Accordingly numbers of transition metal compounds were examined as

catalysts. Excess alkali was used to promote sebacic acid. Safer white mineral oil having a

boiling range of 300-4000C was used to reduce the reaction mixtures viscosity and thus

improve mixing. The results of investigations are presented in Table 5.4.

The normally expected theoretical yields of 2-octanol and sebacic acid from alkali

pyrolysis of castor oil containing 84% ricinoleic acid are 35.7 and 43.6%, respectively3.

ZnO exhibited better cracking catalytic effectiveness as shown by the results of batch SB2

(36.7% yield of theoretical output) in comparison to those of uncatalysed batch SB1 (7.6%

yield of theoretical output). The melting point and AV of products were matching to the


189

Table 5.3 Clay catalysed dimerization of soya FA/ FAME and DCO FA

Batch

Dimerization parameters Characterization of crude

Dimerized product

Vacuum Distillation parameters and

results

Catalyst

(wt%)

Temp.

(0C)

Time

(hr)

Steam

pressure

(psig)

AV RI Gardner

Colour

Distillation

pressure,

mm Hg

Distillation

Temp, 0C

% yield of dimer and

trimer

Dimerization of soya FA and FAME

D6 0 230 3 120-140 192.6 1.4765 7 0.5 188-190 13

D7 4 230 3 120-140 190.7 1.4783 7 0.5 180-196 23.5

D8 4 190 3 100 190.7 1.4772 5 0.5 180-194 22.6

D9

(FAME) 5 230 4

Under N2

atmosphere

SV

177.5 1.467 1

1-2 160-190 10

Dimerization of DCO FA-I

D10 0 250 4 160 195.0 1.475 7 1-2 180-200 59

D11 2 230 3 140 192.7 1.479 6 0.5 174-188 60

D12 4 180 3 100 193.4 1.479 5 0.5 174-188 60

Dimerization of DCO FA-II

D13 2 220 3 100-110 200.4 1.49 7 1-2 170-210 63

D14 4 220 3 100-110 198.7 1.492 7 0.5 170-202 65


190

theoretical values of pure sebacic acid. In a similar manner, other transition metal

compounds such as lead mono-oxide (PbO) and BaSO4 demonstrated moderate catalytic

effectiveness similar to that of ZnO (batch SB2). But the overall results were still lower

than the expected industrial breakeven yields (at least 70.0% yield of theoretical output).

Batch SB3 involved the use of heavy white oil as the diluents and an

environmental friendly nano zinc oxide catalyst. When ZnO was obtained in nanoform

(refer section 5.2 and Fig. 5.1 and 5.2 for further details), the catalytic activity for

oxidation of aldehyde to decanoic acid and selectivity of suppressing the other forward

reaction of hydrogenation of aldehyde were found to be enhanced as demonstrated by the

results. Sebacic acid yield of 79.6% of theoretical output and the purity of 99.0% after

separation and recrystalisation (based on NMR analysis) were attained.

Fig. 5.4 and Fig. 5.5 presented the overlay FTIR and NMR spectra, respectively of

purified sebacic acid obtained from batch SB3. In Fig. 5.4, the band at 1744 cm-1

is

assigned to the C=O stretching vibration of the carboxylic groups of sebacic acid. NMR

spectrum depicted in Fig. 5.5 confirmed the formation of sebacic acid on the basis of

matching of same with NMR of standard sebacic acid. δ 2.3 ppm corresponded to the

proton adjacent to carbonyl group (α proton) while δ 1.6 ppm and δ 1.3 ppm are related to

β proton and γ proton, respectively. δ 0.9 ppm is related to δ protons. Overlay FTIR

spectra of 2- octanol obtained from three different batches (SB1-3) are presented in Fig.

5.6. It displayed the broad peak at 3342 cm-1

corresponding to the stretching frequency of

OH group which thus conformed the formation of 2-octanol.

Table 5.4 Alkali fusion of sodium ricinolate

Diluent:Paraffin oil (Heavy):NaOH:Na ricinoleate::2:1:6

Batch

code

Reaction parameters Characteristics of sebacic

acid

Characteristics of

2-octanol

T, 0C

Time,

hrs

Catalyst

@ 0.5%

by wt.

Acid

value

Melting

point, 0C

% Yield

Boiling

point, 0C

%Yield

SB1 250 6 -- 523 132 2.7 180 2.4

SB2 250 6 ZnO 526 128 13.1 180 9.6

SB3 250 6 nano

ZnO

530 130 28.4 180 20.7


191

Fig. 5.4 FTIR overlay of sebacic acid

Fig. 5.5 1HNMR spectrum of sebacic acid (batch SB3)


192

Fig. 5.6 FTIR overlay of 2-octanol

Thus using nano zinc oxide as the catalyst and heavy white mineral oil as the

diluent, a clean preparation process of sebacic acid by alkaline cracking ricinoleic acid

was established.

References:

1 Barret, F. O.; Goebel, C. G.; Peters, R. M.; Springdale; Cincinnati; Ohio. U.S.Patent,

1957, 2,793,220.

2 U.S.Patent, 1998, 6,429,324 B1.

3 Vasishtha, A.K.; Trivedi, R.K.; Das, G. J. Am. Oil Chem. Soc.,1990, 67, 5, 333-337.

4 Logan, R. L.; Udeshi, S.V. U.S.Patent, 2002, 6,392,074 B1.

5 Azcan, N.; Demirel, E. Ind. Eng. Chem. Res. 2008, 47, 1774-1778.

6 Wang, Y.; Zhang, X.; Li, H.; Dou, K.; Zhang, T.; Yao, N. Industrial Catalysis, 2012, 20,

4, 68-71.

7 Mishra, S.; Kulkarni, R. D.; Patil, U. D.; Ghosh, N. Indian Patent, 2009, 235186.


193

8. Breuer, T.E. Kirk-Othmer (ed) Encyclopedia of Chemical Technology, John Wiley &

Sons, 4th

Ed., New York, 1979, 7, 768-782.

9. Cecehi, G.; Biasini, S.; Ucciani, E.; Perrin, J.L. Rev. Franc. Corps Gras., 1986, 33, 12,

483- 487.

10. Kyenge, B.A. M.Sc. Thesis, 2006, University of Nigeria, Nsukka.

11. Jonah, T. A.; Paul, M.; Ejikeme, J. A.; Ibemesi. International Journal of Physical

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* * * * *

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Chapter 5 Dimerization of unsaturated fatty acids/ methyl ...shodhganga.inflibnet.ac.in/bitstream/10603/25187/2/13. chapter 5.pdf · Ph. D. Thesis, Priya S. Deshpande, NMU, Jalgaon,